This invention relates generally to internal combustion engines having processor-based electronic controls that control the operation of electric-actuated fuel injectors that inject fuel into engine combustion chambers. More particularly the invention relates to an improvement in the compensation of signals for operating the fuel injectors at engine starting and initial running, such as at a cold start.
A known electronic engine control system comprises a processor-based engine controller that processes various data to develop fueling data for the engine. The fueling data represents an amount of fuel that is to be introduced into the engine for combustion. A known control system further includes an injector control, or injector driver, module for operating fuel injectors that inject fuel into the engine in amounts corresponding to the fueling data. The fueling data is supplied to the injector control module from the engine controller, and the injector control module may have its own processor for making certain adjustments to the supplied data to develop proper data for causing the fuel injectors to inject fuel in amounts corresponding to the fueling data calculated by the engine controller. Adjustment may be made for any one or more of various reasons, certain of which will be discussed herein in connection with disclosure of the present invention.
The injector control module also comprises injector drivers each of which delivers an electric current signal to an electric actuator of the respective fuel injector to cause an injection of fuel. The signal that is applied to a fuel injector actuator from the respective driver is typically a pulse width modulated signal wherein the width of each applied pulse essentially determines the amount of fuel that the fuel injector injects into the corresponding engine cylinder in consequence of that pulse.
One reason for the injector control module to make an adjustment of the fueling data that is supplied to it is to compensate for certain characteristics of the specific fuel injectors. Another reason is to compensate for certain prevailing conditions such as state of the engine and ambient effects, such as temperature.
When the fueling data received by the injector control module represents the width of an electric pulse that is intended to cause a corresponding amount of fuel to be injected, the ability to successfully start an engine may involve a modification of that fueling data to cause the actual pulse width applied to a fuel injector to differ from the width that corresponds to the received fueling data. For example, the fueling data supplied to the injector control module may represent a certain pulse width based on a particular set of prevailing conditions. However, a set of conditions that prevail when an engine is being cranked, then starts, and then begins to run, may be sufficiently different from the set on which the calculated fueling data is premised that the supplied fueling data must be adjusted by the injector control module in order to assure that the actual fueling indeed corresponds to the supplied fueling data.
A prior method for adjusting the fueling data for such conditions comprises using a steady state multiplier based on injection control pressure and on engine oil temperature as a measure of engine operating temperature. While multiplication of pulse width by such a multiplier may be effective for cranking and initial starting of an engine over a range of temperatures, it requires some adjustment as the engine begins to run and warms up.
The present invention relates to an engine control system that comprises a processor, wherein the processor calculates desired fueling data for an engine and a multiplier is used to adjust, or compensate, the calculated fueling data before that data is allowed to act on a fuel injector. The invention comprises a novel strategy for modifying and using the multiplier in a way that accounts for various conditions that affect the cranking, starting, and initial running of an engine so that the fuel actually injected more closely corresponds with the calculated fueling data for various sets of prevailing conditions that could otherwise cause actual fueling to differ significantly from desired fueling. The invention also accounts for changing fuel injector characteristics as they warm up.
Without the present invention, an engine control system may experience a situation during initial engine running where the influence of the governor portion of the control system on the fueling data calculation may cause rather substantial variation in the fueling data, including periodically calculating zero fueling. This substantial variation in calculated fueling data in turn may cause substantial variation in engine idle speed as the engine warms up. Such substantial variation in engine idling is considered undesirable, especially in an automotive vehicle, because the driver may consider it objectionable or even perceive it as a problem with the engine. With the present invention the calculated fueling data does not fluctuate over as wide a range, and as a result, there is less fluctuation in engine idle speed as the engine warms up.
A generic aspect of the present invention relates to an internal combustion engine comprising a processor-based engine control system, and a fueling system that fuels the engine under control of the engine control system. The control system processes data to develop desired fueling data representing a desired amount of fuel for fueling the engine, modifies the desired fueling data by a multiplier during cranking, starting, and initial running phases of the engine, causes the fueling system to fuel the engine according to the modified desired fueling data during the cranking, starting, and initial running phases of the engine, and thereafter modifies the multiplier by a multiplier adder and causes the fueling system to fuel the engine according to the modified desired fueling data as further modified by the multiplier adder. Another generic aspect relates to this method of fueling the engine.
Still another generic aspect relates to an internal combustion engine comprising a processor-based engine control system, and a fueling system that fuels the engine under control of the engine control system. The control system processes data to develop desired fueling data representing a desired amount of fuel for fueling the engine, modifies the desired fueling data by a modifier and causes the fueling system to fuel the engine according to the modified desired fueling data during cranking, starting, and initial running phases of the engine, and thereafter further modifies the modifier by a further modifier derived from averaging desired fueling data taken over a time interval that includes time prior to the initial running phase of the engine and causes the fueling system to fuel the engine according to the further modified modifier. Another generic aspect relates to this method of fueling the engine.
The foregoing, along with further features and advantages of the invention, will be seen in the following disclosure of a presently preferred embodiment of the invention depicting the best mode contemplated at this time for carrying out the invention. This specification includes drawings, now briefly described as follows.